Optical disk, and information recording/reproduction apparatus

Abstract: In an optical disk having a recording plane having a spiral first track and a spiral second track, information being to be recorded into and/or reproduced from said first and second tracks, the first track is formed into a groove-like shape, the second track is formed between adjacent the first tracks and into a land-like shape, and the first and second tracks record informations in different modulation methods.

Description: The invention relates to a high density optical disk and to a method of tracking such disk, as set forth in the preamble of claim 1. A disk of this kind is known from US 5,199,022. This document describes an optical disk with a land and a groove track wherein the address is divided into a high and a low address group for distinguishing the tracks from each other. The address group is evaluated in a land or groove tracking control. US 5,185,730 discloses an optical disk and a method for writing data to and reading data from said disk that has address information written on a land disposed between grooves or in its pre-grooves. Because data is written to and read from the pregrooves or land where no address is written, continuous signals can be written to and read from the disk without format change. The pregrooves guide the beam spot for writing and reading data, the pregrooves flanking the land containing address information. The method involves generating a control signal for controlling the polarity and level of the direction and amount of deviation of the beam spot directed at the land (or pregrooves). In accordance with the control signal, the beam spot is made to follow the land (or pregrooves) while reading address information therefrom. Capacities of typical optical disks are as follows: when an optical head of a lens NA of 0.5 is used, a 130-mm disk has a capacity of 300 to 500 MB per face, and a 90-mm disk has a capacity of about 128 to 250 MB per face. For multimedia purpose, a high density recording/reproduction technique which uses a short-wavelength laser of 680 nm to obtain a capacity that is about 2 to 4 times the above-mentioned capacities has been studied. Fig. 10 shows plan views (upper ones) and section views (lower ones) of continuous servo track formats in the prior art. Fig. 10(a) shows a continuous servo track which is employed in a 130-mm or 90-mm optical disk of the prior art and which is of a land record track format. In the land record track format, a track consists of a groove 2 which is formed on a transparent substrate 1 and which has a depth of λ/(8·n) (λ is the wavelength of a laser, and n is the refractive index of the substrate 1. The same applies to the followings.), and pits 4 constituting a sector identification (ID) signal, and record marks 5 are recorded onto a land 3 sandwiched by the tracks. The pits 4 for the ID signal are convex-concave pits having a phase depth of λ/(4·n). The track pitch is selected so as to be about λ/NA which is obtained from the laser wavelength (λ) and a lens aperture (NA). In the prior art disk, since the lands must remain to exist between the grooves 2 and the ID signal pits 4, it is difficult to reduce the track pitch to 1.3 µm or less in the view point of a land forming process. Fig. 10(b) shows an example of a groove record track format in which tracks are formed by simple grooves 6 having a phase depth of λ/(8 N n) and lands 7, and pits 8 constituting an ID signal and record marks 9 wherein data signals are recorded are recorded into the grooves 6. Since such a groove record track has a track structure consisting of the simple grooves 6, a disk of a track pitch which is 1 µm or less can easily be produced. Fig. 10(c) shows an example of a land/groove record track format in which groove record tracks are formed by setting the width of grooves 11 having a depth of about λ/(8·n) to be one-half of the track pitch, and signals 12 are recorded also onto lands 10. In principle, this land/groove recording can achieve an area recording density which is twice that of the land recording of Fig. 10(a). Generally, when a track pitch is to be reduced, there arise problems in a cross-talk of a signal recorded in an adjacent track, in a cross-erase in which also signals into two adjacent tracks are erased by conducting a data recording, and in the stability of a tracking servo. The stability of a tracking servo will be discussed. In the land record track 10 for the land/groove recording of Fig. 10(c), the track pitch is one-half of λ/NA. In the case where λ is 830 nm and NA is 0.5, even when the pitch of tracks for recording signals is 0.8 µm, the tracking servo can be conducted with respect to the track pitch of 1.6 µm consisting of each groove and land. Consequently, the tracking can be done stably by either of the 3-beam method and the push-pull method which are conventionally employed. Even in the land/groove recording in which recording is conducted as described above, when the track pitch is further reduced in order to increase the recording density, there arises a problem in that a cross-talk between the track of the groove 11 and that of the land 10 occurs. Specifically, in the case where an optical head in which the laser wavelength λ is 830 nm and the lens aperture NA is 0.5 is used, a cross-talk of -30 to -35 dB occurs when the track pitch is 1.6 µm, and that of -15 to-20 dB occurs when the track pitch is 0.8 µm, thereby producing a problem in that an ID signal and a data signal cannot be reproduced normally. Particularly, there arise the following problems: In a track search process, the confirmation of a target track is made difficult by reproduction errors such as that an ID signal is caused to be erroneously reproduced by an effect of a cross-talk on the ID signal, and that an ID signal of an adjacent track is erroneously reproduced. In a recording process conducted on an unrecorded sector, even when an ID signal leaks from an adjacent track, the reproduction is apparently conducted in a normal manner, thereby causing data to be recorded into a wrong sector. In the groove/land recording conducted as described above, however, the track density is doubled, and hence there arises a problem in that, in a recording or reproducing process, a cross-talk, or a cross-erase produces errors which exceed a criterion, so that defective sectors are generated in an increased number. It is the object of the invention to provide an optical disk which provides a facilitated distinction between a land or a groove track. The above object is achieved by the subject matter of claim 1. Preferred embodiments of the invention are described by the subject matter of the dependent claims. In an aspect of the invention the recording density as compared with those of the prior art is increased and the level of a cross-talk between tracks of a land and a groove are reduced and errors occurring in a recording or reproduction of an ID signal or a data signal by a cross-talk between tracks of a land and a groove are prevented. Fig. 1 is a diagram showing the sector format of an optical disk which is a first embodiment of the invention. Fig. 2 is a diagram showing the sector format of an optical disk which is a second embodiment of the invention. Fig. 3 is a diagram showing the sector format of an optical disk which is a third embodiment of the invention. Fig. 4 is a diagram showing the format of an ID signal and the arrangement of an optical disk which is a fourth embodiment of the invention. Fig. 5 is a block diagram of an embodiment of an information recording/reproduction apparatus which is to be applied to the optical disk of the invention. Fig. 6 is a block diagram of an embodiment of a focus tracking control circuit of the embodiment. Fig. 7 is a block diagram of an embodiment of a sector ID reproduction circuit of the embodiment. Fig. 8 is a block diagram of another embodiment of the sector ID reproduction circuit of the embodiment. Fig. 9 is a block diagram of an embodiment of a sector recording/reproduction control circuit of the embodiment. Fig. 10 is a diagram illustrating an information recording conducted on an optical disk of the prior art. Fig. 1 is a diagram showing the sector format of a land/groove record optical disk which is a first embodiment of the invention. In Fig. 1, (a) shows the sector format of a groove record track which functions as the first track. A sector 13 consists of a sector ID field ID1 in which address signals A1 and A2 for the sector and modulated by a first modulation method are recorded, a data field DF in which data are recorded in a second modulation method, a gap G1 in which no signal is recorded, and a buffer field B1 for absorbing variations of the disk rotation and various time periods. The data field DF includes a synchronous clock field VFO 14 for pulling a clock signal, a data mark SYN 15 indicating the beginning of data, and user data and error correction codes 16. Fig. 1(b) shows the sector format of a land record track which functions as the second track. A sector 17 consists of a sector ID field ID2 in which address signals a1, a2 and a3 for the sector are recorded in the second modulation method, a data field DF in which data are recorded in the second modulation method, a gap G2, and a buffer field B2. The data field DF has the same configuration as that of Fig. 1(a). In Fig. 1, for example, the PE (Phase Encoding) modulation which is a digital modulation method is employed as the first modulation method, and, for example, the (2-7) RLL (Run Length Limited) modulation which is a digital modulation method is employed as the second modulation method. Since the DR (Density Ratio) of the modulation methods is 1 : 3 and the reproduction of an RLL signal requires a PLL (Phase Lock Loop) circuit, an address signal is written twice in ID1 and thrice in ID2 so that the sectors 13 and 17 have the same length. The ID1 and ID2 of the sectors 13 and 17 are arranged in a radial direction of the disk, and a cross-talk of about -15 dB occurs between the ID fields. Since the modulation methods of ID1 and ID2 are different from each other and ID1 and ID2 signal reproduction circuits operate in different modulation methods, however, respective ID signals can normally be reproduced without being affected by a cross-talk. In Fig. 1, only the ID fields of the groove record track and the land record track are subjected to recordings of different modulation methods. Alternatively, also the ID fields and the data fields may be subjected to recordings of different modulation methods. When at least the ID fields among the ID fields and the data fields are subjected to recordings of different modulation methods, the same effect can be attained. Fig. 2 is a diagram showing the sector format of a land/groove record optical disk which is a second embodiment of the invention. In Fig. 2, the same reference numerals as those of Fig. 1 designate blocks having the same functions. In Fig. 2, ID3 and ID4 designate sector identification fields in which address information is recorded. The sector format of a groove record track shown in Fig. 2(a) is the same as that of a land record track shown in Fig. 2(b). In the sector identification fields ID3 and ID4, signals which are modulated by the same modulation method are recorded so as to be opposite in polarity to each other. Specifically, in ID3, as shown in Fig. 2(a'), "1" of a channel bit of a modulated signal is recorded at the level of the land, and "0" at the level of the groove. In ID4, as shown in Fig. 2(b'), "1" of a channel bit is recorded at the level of the groove, and "0" at the level of the land. The ID3 and ID4 of the sectors 13 and 17 are arranged in a radial direction of the disk, and a cross-talk of about -15 dB occurs between the ID fields. Since the ID signals in the land and the groove are opposite in polarity to each other, however, an ID signal reproduction circuit can read only an ID signal which has undergone a signal inversion process corresponding to the respective track, and therefore normally reproduce the respective ID signal without being affected by a cross-talk. Fig. 3 is a diagram showing the sector format of a land/groove record optical disk which is a third embodiment of the invention. In Fig. 3, (a) shows the sector format of a groove record track. The track 18 is divided into a plurality of sectors 19. Fig. 3(b) shows the sector format of a land record track. The track 20 is divided into a plurality of sectors 21. Fig. 3(c) shows the format of sector ID fields ID of the sectors 19 and 21. Each sector ID field consists of a VFO2 for clock synchronization, an address mark AM indicating the beginning of address information, a track address TA, a sector address SA, a land/groove identification signal 22, an error detection signal CRC, and a postamble PA. In Fig. 3, the initial sector 19 of the groove record track 18 is positionally shifted from the initial sector 21 of the land record track 20 by a distance G3, so that IDs of the sectors do not overlap with each other in the track direction. The land/groove identification signal 22 of each sector indicates whether the corresponding ID belongs to the groove record track 18 or to the land record track 20. For example, when the ID belongs to the groove record track 18, "0" is recorded, and, when the ID belongs to the land record track 20, "1" is recorded. Since the IDs of the tracks 18 and 20 are arranged in a radial direction of the disk with being positionally shifted by G3, they are not mutually affected by a cross-talk. Even when a cross-talk occurs, the ID signal of the track which is currently tracked by the light beam is allowed to be normally reproduced, by checking the land/groove identification signal in the ID signal reproduction circuit. Since the ID signals are shifted in the track direction, also an effect that pits in the ID fields can easily be formed is produced. Fig. 4 is a diagram showing the arrangement of signals in a land/groove record optical disk which is a fourth embodiment of the invention. In Fig. 4, (a) shows the configuration of an address signal of each sector which is used in the embodiment. The configuration is the same as that shown in Fig. 3(c). Fig. 4(b) shows the relationship of the recording positions of the VFO2 fields which are respectively at the beginnings of the ID signals of a groove record track 23 and a land record track 24. Record pits 25 of a channel bit "1" of the address signal of the groove record track 23 are formed so as to correspond to the level of a land 28, and "0" is formed so as to correspond to the level of a groove 29. Record pits 26 of the address signal of the land record track 24 are formed in such a manner that a channel bit "1" corresponds to the level of the groove 29, and "0" to the level of the land 28. Also in the first and third embodiments, the pits 25 and 26 may be formed in a similar manner as described above. In the embodiment, the pits 25 and 26 are recorded with being shifted by one-half of the maximum frequency period T of the address signal, or so as to form a checkered pattern. Since the record pits of the address signals of the tracks 23 and 24 are arranged in a radial direction of the disk with being positionally shifted by T/2, the influence of a cross-talk can greatly be suppressed. Even when an address signal is erroneously reproduced by a cross-talk, the ID signal of the track which is currently tracked by the light beam is allowed to be normally reproduced, by checking the land/groove identification signal 22. In the first to fourth embodiments described above, the address signal may be composed of one of the following sets: the track address TA, and the sector address SA; the track identification signal 22, the address information AM, and the error detection signal CRC; and the track address TA, the sector address SA, the track identification signal 22, the address information AM, and the error detection signal CRC. The optical disks described in the first to fourth embodiments are generally formed so that the depth of the groove record track is set to be λ/(8·n)where λ is the wavelength of a laser beam, and n is the refractive index of the disk substrate. Fig. 5 is a view showing the configuration of an embodiment of an information recording/reproduction apparatus by which information is recorded onto and/or reproduced from the optical disk of the invention. Hereinafter, the description is made while setting the track designation means as a CPU 47, the track search means as a linear motor 34, the signal reproduction means as a head amplifier 36, the address reproduction means as a sector ID reproduction circuit 40, the data recording/reproduction control means as a sector recording/reproduction control circuit 41, and the information recording/reproduction means as a data modem circuit 42. In Fig. 5, 30 designates an optical disk which is to be attached to a motor 31 so as to be rotated thereby, 32 designates a recording plane of the optical disk 30, 33 designates an optical head for focusing a laser beam on the recording plane 32, and 34 designates the linear motor (LM) which functions as the track search means, and which moves the optical head 33 to search a target track. The reference numeral 35 designates a focus tracking control circuit which consists of focus means for conducting a focus control of the light beam of the optical head 33, and tracking means for conducting a tracking control and a track retrace. The reference numeral 36 designates the head amplifier which functions as the signal reproduction means, and which amplifies and outputs a tracking error signal n and a reproduced signal c in a detection signal a from the optical head 33. The reference numeral 37 designates a binary coding circuit for binary-coding the reproduced signal c, 38 designates a laser driving circuit which drives a semiconductor laser of the optical head 33, and 39 designates a linear motor control circuit which controls the linear motor 34 so that the optical head 33 seeks the target track. The reference numeral 40 designates the sector ID reproduction circuit which functions as the address reproduction means, and which outputs the sector address e and the land/groove identification signal q of the track of a sector ID, from an output d of the binary coding circuit 37. The reference numeral 41 designates the sector recording/reproduction control circuit which functions as the data recording/reproduction control means, which compares the track sector address e with a target sector address of a CPU data bus f at which data are to be recorded or reproduced, to check whether they coincide with each other or not, and which generates a write gate signal g and a read gate signal h for the sector. The reference numeral 42 designates the data modem circuit which functions as the information recording/reproduction means, which conducts a digital modulation on coded data i with the (2-7) RLLC (Run Length Limited Code) or the like and outputs a modulated signal j, and which demodulates the binary-coded reproduced signal d and outputs demodulated data k. The reference numeral 43 designates an error correction circuit which generates coded data i wherein an error correction code is added to data to be recorded, and which detects an error in demodulated data k to correct the data, 44 designates a memory for temporarily storing data, 45 designates a host computer, 46 designates an interface IF to which the host computer 45 is connected through a SCSI (Small Computer System Interface) bus x, and 47 designates the CPU of a microcomputer which functions as the track designation means, and which controls the whole of the information recording/reproduction apparatus. In Fig. 5, m designates a land/groove selection signal which is output from the CPU 47 and supplied to the focus tracking control circuit 35 and the sector ID reproduction circuit 40, and which selects one of the recording/reproduction on the land record track and that on the groove record track. Fig. 6 is a view showing the configuration of a tracking control unit of the focus tracking control circuit 35 of Fig. 5. In the figure, 48 designates a polarity inversion circuit for the tracking error signal n, 49 designates a multiplexer MPX which selects the tracking error signal n or an inverted signal n' of the error signal in accordance with the land/groove selection signal m, 50 designates a tracking servo circuit, and p designates an actuator driving signal for driving a tracking actuator of the optical head 33. The land/groove selection signal m is switched and the polarity of the tracking error signal n is inverted, so that the tracking is conducted on the land record track or the groove record track. Fig. 7 is a view showing the configuration of the sector ID reproduction circuit 40 which is used when, in the optical disk of the first embodiment of Fig. 1, the signal modulation method of the sector ID field of the land record track is different from that of the groove record track. In the figure, 51A designates an address reproduction circuit A which reproduces the sector ID of the groove record track, 51B designates an address reproduction circuit B which reproduces the sector ID of the land record track, and 52 designates a multiplexer MPX which selects either of reproduction address outputs e1 and e2 of the address reproduction circuits 51A and 51B in accordance with the land/groove selection signal m. Fig. 8 is a view showing the configuration of the sector ID reproduction circuit 40 which is used when, in the optical disk of the second embodiment of Fig. 2, the modulated signals of the sector ID fields of the land and groove record tracks are inverted in polarity with respect to each other. In the figure, 53 designates an inverting circuit which inverts the polarity of the binary-coded reproduced signal d, and 54 designates a multiplexer MPX which selects the binary-coded reproduced signal d or an inverted signal d' of the reproduced signal in accordance with the land/groove selection signal m, 55 designates an address reproduction circuit, and q designates the land/groove identification signal. In the circuit of Fig. 8, when, in the optical disk of the third embodiment of Fig. 3, the IDs of the groove record track 18 and the land record track 20 which are disposed so as not to positionally overlap with each other and recorded in the same modulation method are to be reproduced, the land/groove selection signal m is set so that the multiplexer 54 selects the binary-coded reproduced signal d, whereby the land record track or the groove record track is identified with using the land/groove identification signal q and combining the circuit with that of Fig. 9 which will be described below. Fig. 9 is a view showing in detail the configuration of the sector recording/reproduction control circuit 41 which is applied to the optical disks shown in Figs. 3 and 4. In the figure, 56 designates a register which latches the target address of the CPU data bus f in response to a strobe s1, 57 designates a comparator circuit A which compares an output of the register 56 with the reproduction address e, 58 designates a comparator circuit B which compares the land/groove identification signal q with the land/groove selection signal m and outputs a coincidence signal when the two signals coincides with each other under the state where the comparator circuit A 57 outputs a coincidence signal, and 59 designates a read/write gate generator which outputs at the timing of the output of the comparator circuit B 58 a read or write command that has been latched in a register 60 from the CPU data bus f in response to a strobe s2, as the write gate g or the read gate h to the data modem circuit 42. The operation of the recording/reproduction apparatus which is configured as described above and records and/or reproduces information on a double sided optical disk will be described. Hereinafter, the data record operation will be described. The host computer 45 outputs the write command to the SCSI bus x. The CPU 47 receives the command through the IF 46 to interpret it. Depending on whether the target track is the land record track or the groove record track, the CPU 47 outputs the land/groove selection signal m so that the optical head 33 conducts the focus tracking on the given record track. As shown in Fig. 6, the focus tracking control circuit 35 makes the polarity of the tracking error signal n inverted or non-inverted which is supplied from the optical head 33 depending on the land/groove selection signal m, and supplies the actuator driving signal p to a tracking actuator coil of the optical head 33. The focus tracking control circuit then supplies a seek command for the target track to the linear motor driving circuit 39 to drive the linear motor 34, thereby moving the optical head 33 to the target track. Data to be recorded which are supplied from the host computer 45 are once stored in the memory 44. The error correction circuit 43 outputs the coded data i wherein an error correction code is added to the data to be recorded. The CPU 47 sets a record sector address and the record command into the sector recording/reproduction control circuit 41 which in turn compares the record sector address with the address output e of the ID reproduction circuit 40. When the given sector is detected as a result of coincidence of the addresses, the write gate signal g is supplied to the data modem circuit 42. The write gate g actuates the data modem circuit 42 so that the coded data i are modulated with the (2-7) RLL, and the modulated signal j is supplied to the laser driving circuit 38. The optical head 33 records the modulated signal j into the sector of the recording plane 32. The above data record operation is repeated in the given number of sectors. Hereinafter, the data read operation will be described. The host computer 45 outputs the read command to the SCSI bus x. The CPU 47 receives the command through the IF 46 to interpret it. Depending on whether the target track is the land record track or the groove record track, the CPU 47 outputs the land/groove selection signal m so that the optical head 33 conducts the focus tracking on the given record track. As shown in Fig. 6, the focus tracking control circuit 35 makes the polarity of the tracking error signal n inverted or non-inverted which is supplied from the optical head 33 depending on the land/groove selection signal m, and supplies the actuator driving signal p to the tracking actuator coil of the optical head 33. The focus tracking control circuit then supplies a seek command for the target track to the linear motor driving circuit 39 to drive the linear motor 34, thereby moving the optical head 33 to the target track. The CPU 47 sets a read sector address and the read command into the sector recording/reproduction control circuit 41 which in turn compares the read sector address with the address output e of the ID reproduction circuit 40. When the sector recording/reproduction control circuit 41 detects the given sector as a result of coincidence of the addresses, the read gate signal h is supplied to the data modem circuit 42. The data modem circuit 42 is actuated in response to the read gate h, and demodulates the detection signal d detected by the optical head 33, to obtain the reproduced data k. The reproduced data k are then stored in the memory 44. The reproduced data which are stored in the memory 44 are subjected to the error detection and correction in the error correction circuit 43, and again stored in the memory 44. The reproduced data which have undergone the error correction are transferred to the host computer 45 through the interface 46. The above data read operation is repeated in the given number of sectors. The operations of the ID reproduction circuit 40 and the sector recording/reproduction control circuit 41 will be described in detail while comparing them with the embodiments of the optical disks of the invention to which the circuits are applied. To the optical disk of the first embodiment (Fig. 1), applied is the ID reproduction circuit 40 having the configuration shown in Fig. 7. In the optical disk of Fig. 1, the ID fields of the land record track and the groove record track are modulated in different modulation methods and recorded. In Fig. 7, therefore, the first and second address reproduction circuits 51A and 51B simultaneously conduct the reproduction operation on the binary-coded reproduced signal d. When the modulation method of the binary-coded reproduced signal d coincides with the modulation methods of the first and second address reproduction circuits 51A and 51B, the reproduced address signals e1 and e2 are output. One of the address signals e1 and e2 which corresponds to the land/groove selection signal m is selected by the multiplexer 52 and then output as the reproduced address signal e. To the optical disk of the second embodiment (Fig. 2), applied are the ID reproduction circuit 40 having the configuration shown in Fig. 8, and the sector recording/reproduction circuit 41 having the configuration shown in Fig. 9. In the optical disk of Fig. 2, the address signals of the ID fields of the land record track and the groove record track are recorded in such a manner that they are opposite to each other in polarity. In Fig. 8, the multiplexer 54 selects one of the binary-coded reproduced signal d and the binary-coded reproduced signal d' which has been inverted by the inverting circuit 53, in accordance with the land/groove selection signal m. The selected signal is demodulated by the address reproduction circuit 55 which in turn outputs the reproduced address signal e and the land/groove identification signal q to the sector recording/reproduction control apparatus 41 of Fig. 9. In Fig. 9, the target address of the CPU data bus f is latched in the register 56 in response to the strobe s1, and compared with the reproduced address signal e in the comparator circuit 57. The land/groove identification signal q is compared with the land/groove selection signal m. The write command or the read command of the CPU data bus f is latched in the register 60 in response to the strobe s2, and is processed by AND operation with the output of the comparator circuit 58 so that the write gate g or the read gate h is output. The write gate g or the read gate h is supplied to the data modem circuit 42, thereby actuating the data modulation or the data demodulation. To the optical disk of the third embodiment (Fig. 3), applied are the ID reproduction circuit 40 having the configuration shown in Fig. 8, and the sector recording/reproduction circuit 41 having the configuration shown in Fig. 9. In the optical disk of Fig. 3, the address signals of the ID fields of the land record track and the groove record track are recorded in such a manner that the ID fields do not overlap with each other in the track direction. The reproduction of an address, and the generation of the write gate or the read gate are conducted in the same manner as those applied to the optical disk of the second embodiment, except that the multiplexer 54 in Fig. 8 always selects the binary-coded reproduced signal d. To the optical disk of the fourth embodiment (Fig. 4), applied are the ID reproduction circuit 40 having the configuration shown in Fig. 8, and the sector recording/reproduction circuit 41 having the configuration shown in Fig. 9. In the optical disk of Fig. 4, the address signals of the ID fields of the land record track and the groove record track are recorded in such a manner that pits are shifted by T/2 in the track direction or form a checkered pattern. The reproduction of an address, and the generation of the write gate or the read gate are conducted in the same manner as those applied to the optical disk of the second embodiment, except that the multiplexer 54 in Fig. 8 always selects the binary-coded reproduced signal d. According to the configuration descried above, a cross-talk between land and groove record tracks which are adjacent to each other is reduced as compared with that in the prior art by making the modulation methods and/or the signal polarities different from each other, or changing the positions of IDs or the pit phase, while increasing the recording density of the optical disk of the land/groove recording to a level higher than that of the prior art, whereby data or an ID signal can be read out with a reduced error level and without being affected by a cross-talk. The first to fourth embodiment of the optical disk described above may be combinedly executed in order to attain the object of the invention. According to the configuration in which information is recorded into the first and second tracks in different modulation methods, the recording density can be increased as compared with that in the prior art, and a cross-talk between the first and second tracks can be reduced so that a recording/reproduction error due a the cross-talk between the first and second tracks is prevented from occurring in an ID signal or a data signal. According to the configuration in which information is recorded into the first and second tracks in the same modulation method and in opposite polarities, the recording density can be increased and a cross-talk between the first and second tracks can be reduced so that a recording/reproduction error due to a cross-talk between the first and second tracks is prevented from occurring in an ID signal or a data signal. According to the configuration in which address signals each including address information for identifying the respective track are recorded into the adjacent first and second tracks in such a manner that they do not overlap with each other in a radial direction, the recording density can be increased and a cross-talk between the first and second tracks can be reduced so that a recording/reproduction error due to a cross-talk between the first and second tracks is prevented from occurring in an ID signal or a data signal. According to the configuration in which address signals which are address information are recorded into the adjacent first and second tracks in polarities opposite to each other and in such a manner that they do not overlap with each other in a radial direction, the recording density can be increased and a cross-talk between the first and second tracks can be reduced so that a recording/reproduction error due to a cross-talk between the first and second tracks is prevented from occurring in an ID signal or a data signal. According to the configuration in which when information is to be recorded onto or reproduced from an optical disk, the tracking for the first and second tracks is controlled while the track designation means outputs a tracking error signal obtained from the optical head, to the optical head with inverting the polarity of the signal, information can be recorded onto or reproduced from the optical disk so that the recording density can be increased and that a cross-talk between the first and second tracks can reduced and a recording/reproduction error due to a cross-talk between the first and second tracks is prevented from occurring in an ID signal or a data signal. According to the configuration in which when information is to be recorded onto or reproduced from an optical disk, the address reproduction means compares the output of the track designation means with the track identification signal of the address reproduction means, and, when the output of the track designation means coincides with the track identified by the track identification signal, outputs a reproduction address signal corresponding to the track, information can be recorded onto or reproduced from the optical disk so that the recording density can be increased and that a cross-talk between the first and second tracks can reduced and a recording/reproduction error due to a cross-talk between the first and second tracks is prevented from occurring in an ID signal or a data signal.

Claims: An optical disk comprising a recording surface having a first spiral track (18) and a second spiral track (20), whereby information may be recorded and/or reproduced on or from said first and second tracks, wherein said first track is formed as a groove track(18) and said second track is formed as a land track (20) so that each revolution of said second spiral track is interposed between two adjacent revolutions of said first spiral track(18), characterized in that a sector ID Field comprising address information and an identification signal (22) for identifying the track type is recorded on said first(18) and second (20) track, said sector ID Fields of adjacent portions of said first and second track do not overlap in the track direction. An optical disk according to claim 1, characterised in that the address signal of said first (18) track is of opposite in polarity with respect to the address signal of said second (20) track. An optical disk according to claim 1 or 2, characterised in that the address signal further comprises an error detection signal and an address mark. An optical disk according to one of the claims 1 to 3, characterised in that said first track has a depth of λ/(8·n) where λ is a wavelength of a laser beam, and n is a refractive index of a substrate of said disk. An optical disk according to one of the claims 1 to 4, characterised in that said first (18) and second (20) track are divided into sectors (19, 21) each of which constitutes a unit of recording or reproducing information, a track address (TA) and a sector address (SA) is recorded in the address signal, and information is recorded into and/or reproduced from said sectors (19,21) in a unit of this sector. An optical disk according to one of the claims 1 to 5, characterised in that the address signals of said first and second tracks (18, 20) are constituted by a mark position recording method, the address signal of said first track (18) is recorded in such a manner that a modulated channel bit "1" corresponds to a level of the land and a channel bit "0" corresponds to a level of the groove, and the address signal of said second track (20) is recorded in such a manner that a modulated channel bit "1" corresponds to a level of the groove and a channel bit "0" corresponds to a level of the land.

Inventors: SATOH ISAO, SATOH, ISAO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1994
Main classification: G11B7
IPC codes: G11B20, G11B7, G11B27